OCP Immersion Fluid Requirements Explained
The Open Compute Project (OCP) Immersion Requirements are the main industry reference for immersion cooling fluids. What they ask of a fluid – and what they do not.
Updated 9 November 2026 · Published by IsoTec
What is the OCP Immersion Requirements document?
The Open Compute Project is an industry organisation in which data center operators, hardware manufacturers and suppliers develop open specifications. Within its Advanced Cooling Solutions work, OCP publishes the Immersion Requirements. The document covers single-phase and two-phase immersion: fluids, wetted materials, thermal design, safety and operation. Revision 2.0 dates from January 2022; later OCP documents refer to revision 2.1.
Minimum dielectric requirements
| Property | Unused fluid | Over the fluid lifetime |
|---|---|---|
| Dielectric strength (1 mm gap) | – | ≥ 6 kV |
| Resistivity | ≥ 2.00 GΩ·m | ≥ 0.20 GΩ·m |
| Flash point (COC) | ≥ 150 °C | ≥ 150 °C |
| Auto-ignition temperature | ≥ 250 °C | ≥ 250 °C |
| Sulphur content | < 10 ppm | – |
| Acidity | Limit per fluid class | – |
| Odour (unsealed systems) | ≤ slight | ≤ slight |
Values from Rev. 2.0. Later revisions may differ – always check the current version. The acidity limit differs between hydrocarbons, natural esters, synthetic esters and fluorocarbons, reflecting their chemistry.
Properties a supplier must report
Besides safety and technical data sheets, OCP asks for a summary of fluid properties with defined test methods:
| Property | Test method named by OCP |
|---|---|
| Dielectric strength (1 mm) | ASTM D1816 (IEC 60156) |
| Dielectric constant and loss tangent | At 20 and 40 GHz, at 20 and 70 °C |
| Resistivity | ASTM D1169 |
| Maximum moisture for dielectric breakdown | ASTM D1533 |
| Specific heat capacity | ASTM E1269 |
| Thermal conductivity | ASTM D7896 |
| Density | ISO 12185 |
| Volumetric expansion | ASTM D1903 |
| Kinematic viscosity at 0, 20, 40 and 60 °C | ASTM D7042 |
| Vapour pressure at 60 °C | ASTM D2879 |
| Pour point | ASTM D97 / ISO 3016 |
| Flash point and fire point | ASTM D92 / ISO 2592 |
| Auto-ignition temperature | DIN 51794 / ASTM E659 |
| Sulphur content | ISO 14596 |
| Acidity | IEC 62021 |
| Oxidation stability | IEC 61125 |
| Biodegradability | OECD 301 |
| Global warming and ozone depletion potential | IPCC 2007 / PNNL-16813 |
Which fluid types OCP recommends
The document states that mineral oils should be avoided and that only synthetic oils, synthetic esters or processed natural esters should be used in single-phase systems. For two-phase systems it covers fluorinated fluids.
Fluid quality management
- The supplier must state which tests and intervals are used to monitor fluid quality. Suggested tests include oxidation stability, interfacial tension, particle count, dielectric strength and flash point.
- Mechanically circulated systems should have continuous filtration – rising particle counts can show up as falling dielectric strength.
- Sulphur content should be monitored regularly.
- Local overheating should be avoided; after an overheating event, flash point and resistivity should be checked.
- Open baths should have a lid to limit the air-to-liquid interface.
- Operators must be trained on the properties of every dielectric fluid in the facility.
How to set up monitoring in practice: immersion cooling fluid maintenance and testing.
Component compatibility testing (OCP guideline v1.5)
In June 2026, OCP published version 1.5 of its guideline for material compatibility testing of server components. For single-phase fluids it describes a heat soak at 80 °C ± 2 °C for 14 days in a closed vessel. Materials are checked for changes in mass, volume, dimensions and hardness, plus functional tests; the fluid is checked for appearance, colour, turbidity and sediment and must still meet the Immersion Requirements afterwards. The guideline is non-normative: it does not set acceptance limits or certify compatibility. Details: material compatibility in immersion-cooled servers.
An ASTM specification is on the way
ASTM committee D27 (electrical insulating liquids and gases) is working on a new specification for single-phase liquids used in immersion cooling of data centers (work item WK97110). Its stated rationale: there is no industry standard for these liquids yet.
What “OCP compliant” means
The OCP requirements are not a certification. Suppliers state compliance in a declaration. Ask for the test reports behind each value, check the revision referenced, and qualify the fluid with your own hardware. A checklist: how to qualify an immersion cooling fluid.
Frequently asked questions
What flash point does OCP require for immersion fluids?
A flash point of at least 150 °C (Cleveland open cup), both for the unused fluid and over its lifetime (Rev. 2.0).
Does OCP allow mineral oil for immersion cooling?
The Immersion Requirements state that mineral oils should be avoided and that synthetic oils, synthetic esters or processed natural esters should be used.
Does OCP certify immersion fluids?
No. The requirements define minimum values and reporting; suppliers declare compliance. Compatibility with specific hardware must be tested separately.
Need fluid data for your OCP checklist?
We provide data sheets and test reports for our ester fluids and support your qualification. IsoTec products are supplied to customers outside Germany.